slamdata/slamengine — pull request #511 by sellout (2014-12-19 17:46:53+00:00)
Title: Some fixes along the way to unifying flatten operations.

* fix $unwind merging so it doesn’t trample the not-unwound version on
the other side of the merge (fixes #494),
* change some other merging to the “common source” style @mprescot and I
had discussed before,
* remove an “auto-join” style merge case (and a workflow test for it),
* fix rendering of ShapePreservingBuilder,
* use `unlessConflicts` to make objectConcat more consistent and less
likely to generate nested documents,
* avoid unnecessary duplication of fields when concating/merging two
groups (fixes #474), and
* parameterize freshId on the label (need to extend this to freshName at
some point).